(4) Outdoor classes in the sun should be avoided when the WBGT exceeds
85F or 29C (Heat Category 4).
(5) When the WBGT reaches 88F or 31C (Heat Category 4), strenuous
exercise should be curtailed for all recruits and other trainees with less than 12 weeks
training in hot weather. Hardened personnel, after having been acclimatized each
season, can carry on limited activity at WBGT of 88F to 90F (31C-32C) for periods
not exceeding six hours a day.
(6) When the WBGT index is 90F or 32C (Heat Category 5) and above,
physical training and strenuous exercise should be suspended for all personnel
(excluding essential operational commitments not for training purposes, where the risk
of heat casualties may be warranted).
(7) Wearing of body armor or necessary warfare protective uniforms (for
example mission-oriented protection posture (MOPP) clothing), in effect adds 10F or
6C to the measured WBGT. Limits should be adjusted appropriately.
(8) The optimal doctrine for preventing dehydration and heat illness during
hot weather operation requires three guidelines:
(a) Command drinking of water in the absence of thirst.
(b) Adequate rest and allowing the body to cool itself.
(c) Water cooled to 60-70F and flavored, if necessary, to improve
palatability and acceptance
e. Solar radiation injuries may occur in hot, arid climates; on high mountain
slopes, where intense ultraviolet radiation may be combined with windburn; or in the
Arctic, where snow blindness may result from reflected light glare. Preventive
measures include the wearing of broad-brimmed hats, sunglasses, and lightweight,
loose-fitting, light colored clothing. Moderate tanning is desirable to increase sunburn
resistance, but the exposure time should initially be limited to 5-15 minutes per day and
gradually increased. Dark, intense, long-term tanning should be avoided as a possible
contributing factor to skin cancers.
f. Cold injuries are also a cause of reduced effectiveness and potentially
permanent damage to health. Low temperatures are necessary for the production of
cold injuries; however, freezing temperatures and temperature alone are not required,
nor is a reliable guide for cold injury occurrence. Factors that, in various combinations,
are involved in cold injury include temperature, humidity, wind-speed, and length of
exposure, activity, type and condition of clothing, previous cold injury, race, and
nutritional state. For example, the combined effect of wind and temperature has been
determined and is expressed as an equivalent temperature in the wind chill chart (see
Figure 1-5). This expresses the effective temperature acting upon exposed flesh.